Network devices, such as routers, security devices (e.g., firewalls), switches, or other network devices, may include multiple power supplies for added network device reliability. The power supplies may be redundantly configured so that either of the multiple power supplies may independently power the network device. The power supplies may also be hot-swappable so that one of the redundant power supplies can be replaced without disrupting operation of the network device.
Network devices installed in certain locations may be required to pass environmental design guidelines, such as guidelines stipulated by law or by industry standard. For example, the Network Equipment Building System (NEBS) standard GR-63-CORE is a commonly used set of safety and environmental design guidelines for telecommunications equipment. Under NEBS, during a fire test, the power supply unit under test is set on fire via a gas burn injected into the (horizontal) air flow inlet of one of the power supplies of the network device for 120 seconds. After the injected gas burn, the power supply is required to self-extinguish the fire and flames and burning particles should not exit from the network device.
Network devices with redundant power supplies have an increased risk of failing the NEBS fire test, as one of the redundant power supplies may continue to run and to power fans of the network device. The running fans may stimulate the fire in the power supply being tested.